IMPROVEMENT OF STEEL BRIDGE RATINGS USING AUTOSTRESS CONCEPT: A FEASIBILITY STUDY

In an effort to make the ratings of older bridges compatible with today's increased truck loads, the most cost-effective solution would be to re-rate the bridges using a higher level analysis. The Autostress procedure--a design method that permits continuous steel bridges to experience a partial plastic hinge at the pier, and a subsequential redistribution of moment from the negative region to the positive region, via the Automoment--is one such analysis. The purpose of this research is to see if the Autostress design procedure for new bridges can be easily adapted to an Autostress rating (ASR) procedure for existing bridges. An ASR flow chart was developed and used to rate three bridges--a two span non-composite, a two span composite, and a three span composite. The same bridges were then rated using the Load Factor Rating (LFR) procedure. The two ratings were compared for each bridge to determine if a preliminary upgrading rating factor could be formed. All three bridges were first rated without cover plates in the negative moment region. For the two span non-composite bridge the ASR and the LFR were virtually the same. For the two span composite bridge ASR permitted a 30% increase over LFR. For the three span composite bridge ASR permitted a 17% increase over LFR. The two span composite bridge was then analyzed with negative moment region cover plates and it was established that the LFR increased tremendously while the ASR remained practically the same. The net result was that cover plates caused the ASR to be 4% lower than the LFR. It was concluded that, since most existing continuous steel bridges have cover plates, it is not feasible to develop a preliminary upgrading rating factor of Load Factor rated bridges.

• Corporate Authors:

  University of Florida, Gainesville

  Engineering and Industrial Experiment Station
  Gainesville, FL  United States  32611

  Florida Department of Transportation

  P.O. Box 1029
  Gainesville, FL  United States  32602

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Ellifritt, D S
  • Hampton, M S
• Publication Date: 1988-6

Media Info

• Features: Appendices; Figures; References;
• Pagination: 77 p.

Subject/Index Terms

• TRT Terms: Alternatives analysis; Feasibility analysis; Load factor; Metal bridges; Ratings; Steel bridges; Stresses
• Old TRIS Terms: Autostress
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00479584
• Record Type: Publication
• Report/Paper Numbers: FL/DOT/BMR-88/327, Final Report
• Files: TRIS, USDOT, STATEDOT
• Created Date: Feb 28 1989 12:00AM